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US 9,451,734 B2Granted
Magnetic shielding device and magnetic shielding method
AssigneeSeiko Epson Corporation
InventorsFumihiko Onuma, Shigemitsu Toda, Ryuji Hokari
Life of this patent
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Abstract
A magnetic shielding device includes: a passive shield having an inner space; a first coil that cancels a magnetic field entering in the inner space; a first magnetic sensor that measures the magnetic field entering in the inner space; a second magnetic sensor located in a position farther from the first coil than the first magnetic sensor; and a controller that controls the first coil so that a gradient between a first magnetic field measured by the first magnetic sensor and a second magnetic field measured by the second magnetic sensor be less than a predetermined threshold.
Claims9
A magnetic shielding device, comprising:
- a passive shield housing having an inner space and first and second openings, the passive shield housing extending in a first direction, the first and second openings being located at two ends of the Passive shield housing in the first direction;
- a first coil that is provided around the first opening in which a first magnetic field exists;
- a second coil that is provided around the second opening in which a second magnetic field exists;
- a third coil that is provided inside of the inner space between the first and second coils;
- a driving circuit that applies a first current to the first and second coils to respectively cancel the first and second magnetic fields and that applies a second current to the third coil;
- a first magnetic sensor that measures the first magnetic field so as to output a first value corresponding to the first magnetic field;
- a second magnetic sensor located at inside of the inner space between the first and second openings so that the second magnetic sensor is closer to a center of the inner space than the first magnetic sensor, the second magnetic sensor outputting a second value corresponding a third magnetic field;
- and
- a controller that is configured to calculate a magnetic field gradient between the first and second magnetic sensors based on the first and second values and a distance between the first and second magnetic sensors in the first direction,
- wherein when the controller determines that the magnetic field gradient is equal to or less than a predetermined value, the controller applies the first current to the first and second coils and the second current to the third coil, and
- when the controller determines that the magnetic field gradient is more than the predetermined value, the controller changes one of the first current and the second current to a different current.
8 more elements
A method for controlling a magnetic shielding device, the magnetic shielding device including:
- a passive shield housing having an inner space and first and second openings, the passive shield housing extending in a first direction, the first and second openings being located at two ends of the passive shield housing in the first direction;
- a first coil that is provided around the first opening in which a first magnetic field exists;
- a second coil that is provided around the second opening in which a second magnetic field exists;
- a third coil that is provided inside of the inner space between the first and second coils;
- a first magnetic sensor that measures the first magnetic field so as to output a first value corresponding to the first magnetic field;
- and
- a second magnetic sensor located at inside of the inner space between the first and second openings so that the second magnetic sensor is closer to a center of the inner space than the first magnetic sensor, the second magnetic sensor outputting a second value corresponding a third magnetic field, the method comprising:
- applying a first current to the first and second coils to respectively cancel the first and second magnetic fields,
- applying a second current to the third coil, and
- calculating a magnetic field gradient between the first and second magnetic sensors based on the first and second values and a distance between the first and second magnetic sensors in the first direction,
- wherein when the magnetic field gradient is equal to or less than a predetermined value, the first current is applied to the first and second coils and the second current is applied to the third coil, and
- when the magnetic field gradient is more than the predetermined value, one of the first current and the second current is changed to a different current.
9 more elements
Dependencies are inferred from the claim text.